Invisible near‐infrared thermo‐stimulated luminescence from carbon dots enabled by stepwise energy transfer for concealed information encryption

Abstract Thermo‐stimulated luminescent (TSL) materials capable of near‐infrared (NIR) emission are attractive for optical information storage and anti‐counterfeiting owing to their intrinsic optical memory and concealed thermal readout characteristics. However, most such TSL systems rely on rare‐earth or transition‐metal doping, while fully metal‐free NIR TSL materials remain extremely lacking. Herein, we report the construction of a metal‐free and NIR‐emissive TSL system based on carbon dots (CDs) via a stepwise energy transfer strategy, by decoupling energy storage and emission regulation within a hybrid material architecture. CDs are embedded in a carbon nitride matrix and simultaneously serve as emissive centers and trap‐modulating units, enabling efficient photoinduced energy storage and thermally activated release. By further integrating stepwise Förster resonance energy transfer, intrinsic green TSL is converted into pink and NIR emission without introducing any metal elements. The resulting materials exhibit long‐term charge retention, rewritable optical memory, and highly concealed NIR readout, enabling advanced applications in information storage, encryption, and anti‐counterfeiting.